Cold Storage Compressor Failure to Start / Overload

Question

Accepted Answer

Single phasing — one of three-phase lines open. Check: Measure all three phase currents with clamp meter — one line at 0 A or imbalance >10% indicates single phasing What to do: Inspect electrical circuit — check breaker, wiring, and terminals, then repair open phase. Restore three-phase voltage and current balance before restarting Faulty start capacitor (single-phase system). Check: Measure capacitor capacitance with LCR meter — out of tolerance by ±20% from rated value indicates failure What to do: Replace with capacitor of identical rating (µF and VAC) Overload relay tripped — high load or high ambient temperature. Check: Check overload relay reset button state. Measure current — verify if exceeding rated current. Identify trip cause (high temp, overload, voltage imbalance) What to do: Resolve trip cause (high temperature, excessive load, voltage imbalance), then manually reset. Do not repeatedly reset without fixing the cause High pressure switch activated — poor condensation. Check: Check discharge pressure with high-side gauge — more than 20% above design indicates poor condensation. Check condenser fans and coil cleanliness What to do: Clean condenser coil (wash fins). Restore cooling water flow (water-cooled). Check fan motor. After resolving cause, manually reset high pressure switch and restart Short cycling — starts and stops more frequently than every 6 minutes. Check: Check control panel start history or current monitor for start interval — less than 6 minutes indicates short cycling What to do: Review control logic — set minimum 6-minute start interval. Readjust temperature differential setting to prevent short cycling

Cold Storage Compressor Failure to Start / Overload

Likely causes

Single phasing — one of three-phase lines open

Faulty start capacitor (single-phase system)

Overload relay tripped — high load or high ambient temperature

High pressure switch activated — poor condensation

Short cycling — starts and stops more frequently than every 6 minutes

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